Functions are resulting more and more in today's production environment in which people have to work hand in hand with robots in close spaces. Protection of a person from the robot is in this respect not possible by mechanical protective devices such as fences or barriers, but must rather be transposed into the direct environment of the robot.
To make this kind of cooperation possible in principle, robot manufacturers have developed robots having a force limitation. The maximum force a robot can exert before the movement is automatically stopped can be set here such that a force effect cannot produce serious injury in the event of a collision of the robot with a person. The motor control and the rotary encoder which carry out a positional determination of the robot arm are safety components with corresponding certification.
In addition, when designing the mechanical robot components, care is deliberately taken to provide edge-free, round or soft external contours so that a possible collision force is distributed over as large an area as possible and so that no danger of lacerations or the like can occur.
An increasing prevalence of safe small robots having safe movement controls and force-limited drives reduces the sources of danger to the tool attachment at the end of the robot arm. A problem which has not yet been solved satisfactorily in this respect is the securing of the tool at the robot per se. The tool itself frequently comprises sharp or pointed parts, parts which rotate or which are hot, etc. in order to be able to carry out its function at all. Examples include drills, screws, cutters, blades, grippers having sharp edges for filigree parts, welding guns, soldering tips, etc.
There is thus an increased risk of injury at the tool, even with a safe force limitation of the robot, due to the movement of the tool or of parts having sharp edges. This tool attachment typically has small dimensions and is well localized. At the same time, the great variety of possible tool geometries, the fast movement in a number of degrees of freedom and the demand for fast fitting and changing geometries of the tool attachment represent new demands on a securing solution which existing safety sensors cannot satisfy or can only meet unsatisfactorily.
The region around the tool cannot be secured satisfactorily using the safety sensors present today such as laser scanners or light grids since the available safety sensors are either too large or too heavy to fasten to the robot arm and are too inflexible with respect to the securing geometry.
A further problem frequently results from the radial securing of a single sensor origin such as e.g. occurs in the case of laser scanners and camera systems. In this case, dead zones arise in the view shadow of the tool which have to be covered by further sensors in a complex and/or expensive manner.
Currently available safety sensors are primarily suited for large, free monitored zones of simple geometry, for example a plane, a parallelepiped or a line and are not the correct solution for the complex geometries at a tool either with respect to their construction size or with respect to their flexibility.
Existing securing concepts additionally frequently suffer from the long response times of the safety sensors which result from the complex evaluations of the data, for example of a 3D camera, in particular of a stereoscopic 3D camera, or from a latency of the data and signal transmission. Brief distances between the protected field boundary and the hazard site are only compatible with fast reaction times of sensors and robots.
As long as the existing deficits cannot be eliminated and the hazard sites cannot be satisfactorily secured, greater restrictions result in the applications in which people and robots can work together in cooperation.
EP 2 395 274 B1, for example, discloses a plurality of time-of-flight sensors to monitor a plurality of dimensions for an operating zone. Furthermore, a plurality of time-of-flight sensors are attached to movable sections of the device. In this respect, the safety zones are set in dependence on the speed of the movable section.